Viscosity and zeta-potential of aqueous bentonite suspension with various electrolytes concentration and pH were measured by using a Couette type automatic rotational viscometer and a Zeta Meter, respectively. An isoelectric point does not exist over the experimental pH range.
A system, which has a large zeta-potential, has a small relaxation time β and a small shear modulus 1/α in the Ree-Eyring generalized viscosity equation, i.e., such a system has a small viscosity value, since η=β/α.
In general, a stable suspension system has a large zeta-potential. The stability condition of clay-water suspension can be estimated by viscometric method since stable suspension generally has small viscosity.